For years, my evenings have looked like this: After my kids go to bed, I go back to work. As soon as the last light goes out, I’m down at my laptop, generally working from 9 p.m. to 10:30 p.m. When I’m in crunch mode, having this extra time is key to making everything work.

But earlier this year, while reading a short productivity ebook—Taming the Work Week, by M. R. Nelson—I realized that my second shift was enabling some bad habits. Nelson, a project manager at a biotech, manages 10 to 15 people and a seven-figure budget, but leaves the office at 4:30 p.m. most days.

One of her secrets? "I don’t use web surfing as a filler at the end of the day, nor do I leave early if I find I’ve finished my main tasks 15 minutes before I usually leave, even though no one would notice or care if I left early. I believe in making full use of the ‘small time’ at the end of the day. One of the things I learned from my years as a contractor, charging time in 15-minute increments, is how much you can get done in 15 minutes."

Looking at my days, I could see I was guilty of just this—filling those last minutes with pointless web surfing (let's face it: I do not need whatever tempting deal Rue La La is offering on All Clad pots and pans). Because I knew I could work later, I wasn’t pushing myself to finish the tasks that needed to be done for the next day. But if I did tackle the most urgent tasks in those last 15 minutes, I might not have to turn on the laptop every night. Not all of those 90 minutes at night were productive. Sometimes when the laptop is on, it just stays on. If it never goes on, it might stay off.

The key is to make a list of 15-minute tasks on the docket, so I’ll always know how to use small bits of time well.

So I’ve been trying to figure out what I can get done in 15 minutes. It’s enough time to answer the three to five emails in the pile that actually need to be responded to. It’s enough time to format and schedule a blog post that’s already been written. It’s enough time to send emails to two people I need to interview for a story. It’s enough time to come up with the questions I’ll ask someone in an interview the next morning.

The key is to make a list of 15-minute tasks on the docket, so I’ll always know how to use small bits of time well. If we’re honest, the average work day turns out to have a lot of these 15-minute—or even five-minute—chunks. There’s the space between the end of one phone call and the start of another. There’s the space at the beginning of a meeting that always starts late. There’s time spent waiting for a colleague to finish up a phone call before you go to lunch together.

That’s not to say that people don’t need breaks. But I don’t need a break at the end of the workday, and electing not to take one means I might get a longer—5:30 p.m. to 8 a.m.—break from work more regularly. That’s worth pushing through the last 15 minutes and seeing what I can get done.

Laura Vanderkam is the author of several time management and productivity books, including I Know How She Does It: How Successful Women Make the Most of Their Time (Portfolio, June 9, 2015), What the …